Rest Bouts Research Articles

The effect of an acute bout of exercise on circulating vitamin D metabolite concentrations: a randomised crossover study in healthy adults.

The effect of acute exercise on circulating concentrations of vitamin D metabolites is unclear. To address this knowledge gap, we examined the effect of a bout of treadmill-based exercise versus rest on circulating concentrations of 25(OH)D3, 25(OH)D2, 3-epi-25(OH)D3, 24,25(OH)2D3, 1,25(OH)2D3, and vitamin D2 and D3 in healthy men and women. Thirty-three healthy adults (14 females, 41 (15) years, body mass index 26.2 (3.7) kg/m2, 36.2 (9.2) ml/kg/min; mean (SD)) completed two laboratory visits involving 60min of moderate-intensity treadmill exercise (60% ) versus 60min of seated rest, both in an overnight fasted-state, as part of a randomised crossover design. Venous blood samples were drawn at baseline, immediately (0h), 1h and 24h after the exercise or rest-period. There was a significant time × trial interaction effect for total circulating 25(OH)D (P=0.0148), 25(OH)D3 (P=0.0127) and 1,25(OH)2D3 (P=0.0226). Immediately post-exercise, 25(OH)D, 25(OH)D3 and 1,25(OH)2D3 concentrations were significantly elevated compared to the control resting condition, and 1,25(OH) 2D3 remained significantly elevated 1 h later. Circulating albumin, vitamin D binding protein, calcium and parathyroid hormone were elevated immediately post-exercise. Thus, an acute bout of moderate intensity exercise transiently increases concentrations of circulating 25(OH)D and 1,25(OH)2D3 compared to resting conditions. KEY POINTS: Observational studies suggest that acute exercise might change circulating concentrations of vitamin D metabolites, but this has not been investigated using randomised crossover studies and using robust analytical procedures. In this study, we used a randomised crossover design to examine the effect of a bout of treadmill-based exercise (vs. rest) on circulating concentrations of a wide range of vitamin D metabolites in healthy humans. We show that an acute bout of moderate intensity exercise transiently increases concentrations of circulating 25(OH)D and 1,25(OH)2D3 compared to resting conditions. These findings indicate that regular exercise could lead to transient but regular windows of enhanced vitamin D biological action.

Effect of extended heat stress in dairy cows on productive and behavioral traits

This study evaluates the response of dairy cows to short and extended heat stressing conditions (from 1 to 28 days), as expressed in changes in their behavior. Due to climate change, heat stress and strong heat waves are frequently affecting the productivity and behavior of dairy cows. In the five years under study from 2018 to 2022, two were characterized by extremely strong heat waves occurring in the region analyzed in this study (Northern Italy). The dairy cattle farm involved in this study is located in Northern Italy and includes about 1 600 Holstein Friesian lactating dairy cows. Phenotypic data were provided by the Afimilk system and compromised behavioral and productive traits. Behavioral traits analyzed were activity, rest time, rest bouts, rest ratio, rest per bout and restlessness. Production traits were daily milk yield, average milking time, somatic cell count, fat percentage, protein percentage and lactose percentage. Climate data came from the National Aeronautics and Space Administration/Prediction of Worldwide Energy Resources database. Heat stress was analyzed considering Temperature-Humidity Index (THI) averaged over 28 different time windows of continuous heat stress. Results showed that rest time and milk yield were the two traits most affected by the increased THI. Rest time was immediately affected by high THI, showing a marked decrease already from 1d window and maintaining this all over the other windows. Furthermore, results show that rest time and rest ratio were only slightly negatively correlated with milk yield (−0.14 and −0.15). In addition, heat stress has a different effect depending on parity and lactation stages on the studied traits. In conclusion, the results indicate that heat stress increases activity and compromises milk production, rest time and milk quality traits. Results further suggest that rest time can be a better parameter than activity to describe the effects of heat stress on dairy cattle. The novel approach used in this study is based on the use of different time windows (up to 28 days) before the emergence of undesired THI and allows to identify the traits that are immediately influenced by the undesirable THI values and those that are influenced only after a prolonged heat stress period.

Bouts of rest and physical activity in C57BL/6J mice.

The objective was to exploit the raw data output from a scalable home cage (type IIL IVC) monitoring (HCM) system (DVC®), to characterize pattern of undisrupted rest and physical activity (PA) of C57BL/6J mice. The system's tracking algorithm show that mice in isolation spend 67% of the time in bouts of long rest (≥40s). Sixteen percent is physical activity (PA), split between local movements (6%) and locomotion (10%). Decomposition revealed that a day contains ˜7100 discrete bouts of short and long rest, local and locomotor movements. Mice travel ˜330m per day, mainly during the dark hours, while travelling speed is similar through the light-dark cycle. Locomotor bouts are usually <0.2m and <1% are >1m. Tracking revealed also fits of abnormal behaviour. The starting positions of the bouts showed no preference for the rear over the front of the cage floor, while there was a strong bias for the peripheral (75%) over the central floor area. The composition of bouts has a characteristic circadian pattern, however, intrusive husbandry routines increased bout fragmentation by ˜40%. Extracting electrode activations density (EAD) from the raw data yielded results close to those obtained with the tracking algorithm, with 81% of time in rest (<1 EAD s-1) and 19% in PA. Periods ≥40 s of file when no movement occurs and there is no EAD may correspond to periods of sleep (˜59% of file time). We confirm that EAD correlates closely with movement distance (rs>0.95) and the data agreed in ˜97% of the file time. Thus, albeit EAD being less informative it may serve as a proxy for PA and rest, enabling monitoring group housed mice. The data show that increasing density from one female to two males, and further to three male or female mice had the same effect size on EAD (˜2). In contrast, the EAD deviated significantly from this stepwise increase with 4 mice per cage, suggesting a crowdedness stress inducing sex specific adaptations. We conclude that informative metrics on rest and PA can be automatically extracted from the raw data flow in near-real time (< 1 hrs). As discussed, these metrics relay useful longitudinal information to those that use or care for the animals.

Circadian Variations in Sympathetic Vasoconstriction in Older Adults with and Without Type 2 Diabetes

An impact of the sympathetic nervous system in the higher rate of cardiovascular events in the early morning compared to the evening has been claimed. Augmented sympathetic vasoconstriction increases cardiovascular risk by augmenting pulse pressure and cardiac afterload. Type 2 diabetes (T2DM) further increases sympathetic neurovascular transduction and cardiovascular risk. We assessed whether peripheral vasoconstriction triggered by a standardized sympathetic stressor is augmented at 6am vs 9pm in adults between 50-80 years with type 2 diabetes (T2DM50-80) vs healthy ones (H50-80). Mean values of sympathetic vasoconstrictor responsiveness (SVR), vascular conductance (VC), brachial artery blood flow, and mean arterial pressure were measured on the contralateral forearm over two 5-minute bouts of rest and handgrip-mediated sympathetic stimulation, respectively. Although baseline VC values were lower (p < 0.01) in the morning vs evening in both groups, SVR values in response to sympathoexcitation were similar in H50-80 (-0.43±12.44 vs -2.57±11.63 %, p = 0.73) and T2DM50-80 (+6.64±10.67 vs +5.21±7.64 %, p=0.90), but higher (p<0.01) in T2DM50-80 vs H50-80 at both day hours. Individuals with T2DM reported positive SVR values and VC change-scores, while healthy individuals reported statistically different (p< 0.02) negative SVR values and VC change-scores. Peripheral vasoconstriction triggered by a standardized sympathetic stressor is similar between morning and evening, regardless of T2DM and different baseline VC values. However, peripheral vasoconstriction responsiveness is blunted in individuals with T2DM as handgrip-mediated sympathoexcitation induces vasodilation in the contralateral forearm in adults with T2DM and vasoconstriction in healthy age-matched controls, highlighting a neurovascular response altered by T2DM.

Impact of Interrepetition Rest on Muscle Blood Flow and Exercise Tolerance during Resistance Exercise.

Background and Objectives: Muscle blood flow is impeded during resistance exercise contractions, but immediately increases during recovery. The purpose of this study was to determine the impact of brief bouts of rest (2 s) between repetitions of resistance exercise on muscle blood flow and exercise tolerance. Materials and Methods: Ten healthy young adults performed single-leg knee extension resistance exercises with no rest between repetitions (i.e., continuous) and with 2 s of rest between each repetition (i.e., intermittent). Exercise tolerance was measured as the maximal power that could be sustained for 3 min (PSUS) and as the maximum number of repetitions (Reps80%) that could be performed at 80% one-repetition maximum (1RM). The leg blood flow, muscle oxygenation of the vastus lateralis and mean arterial pressure (MAP) were measured during various exercise trials. Alpha was set to p ≤ 0.05. Results: Leg blood flow was significantly greater, while vascular resistance and MAP were significantly less during intermittent compared with continuous resistance exercise at the same power outputs (p < 0.01). PSUS was significantly greater during intermittent than continuous resistance exercise (29.5 ± 2.1 vs. 21.7 ± 1.2 W, p = 0.01). Reps80% was also significantly greater during intermittent compared with continuous resistance exercise (26.5 ± 5.3 vs. 16.8 ± 2.1 repetitions, respectively; p = 0.02), potentially due to increased leg blood flow and muscle oxygen saturation during intermittent resistance exercise (p < 0.05). Conclusions: In conclusion, a brief rest between repetitions of resistance exercise effectively decreased vascular resistance, increased blood flow to the exercising muscle, and increased exercise tolerance to resistance exercise.

Motor cortex plasticity response to acute cardiorespiratory exercise and intermittent theta-burst stimulation is attenuated in premanifest and early Huntington\u2019s disease

Huntington’s disease (HD) mouse models suggest that cardiovascular exercise may enhance neuroplasticity and delay disease signs, however, the effects of exercise on neuroplasticity in people with HD are unknown. Using a repeated-measures experimental design, we compared the effects of a single bout of high-intensity exercise, moderate-intensity exercise, or rest, on motor cortex synaptic plasticity in 14 HD CAG-expanded participants (9 premanifest and 5 early manifest) and 20 CAG-healthy control participants, using transcranial magnetic stimulation. Measures of cortico-motor excitability, short-interval intracortical inhibition and intracortical facilitation were obtained before and after a 20-min bout of either high-intensity interval exercise, moderate-intensity continuous exercise, or rest, and again after intermittent theta burst stimulation (iTBS). HD participants showed less inhibition at baseline compared to controls. Whereas the control group showed increased excitability and facilitation following high-intensity exercise and iTBS, the HD group showed no differences in neuroplasticity responses following either exercise intensity or rest, with follow-up Bayesian analyses providing consistent evidence that these effects were absent in the HD group. These findings indicate that exercise-induced synaptic plasticity mechanisms in response to acute exercise may be attenuated in HD, and demonstrate the need for future research to further investigate exercise and plasticity mechanisms in people with HD.

Exposure to melamine cyanuric acid in adult mice induced thyroid dysfunction and circadian rhythm disorder

MCA is a halogen-free flame retardant. It can cause damage to other tissues such as the kidneys and liver. However, the effects on the circadian rhythm and thyroid in adult mice have not been studied. In this article, adult male mice received MCA at concentrations of 0, 10, 20, 30 mg/kg. The results showed that the time spending on wheel-running and rest bouts changed in different period after MCA exposure. MCA disrupted the T3 and T4 hormone homeostasis and decreased the expression of thyroid hormone synthesis genes. The histological morphology of the thyroid gland was damaged. It was suggested that MCA exposure caused circadian rhythm disorder and thyroid dysfunction.

Oxidative stress and its impact on skin, scalp and hair.

Oxidative stress is an unbalanced condition in which the tissues of the body are not sufficiently able to counteract either exogenous or endogenous sources of reactive oxygen species. Oxidative stress is strongly associated with ageing, both local and systemic, as well as a wide range of local health conditions. This review focuses on the oxidative stress data known for skin, scalp and hair. This oxidative stress may be the 'currency' by which an unhealthy scalp leads to deleterious consequences to the hair. The ramifications of this scalp oxidative stress to normal hair elongation, retention and replacement are discussed.

Acute Exercise Modulates the Excitability of Specific Interneurons in Human Motor Cortex

Acute exercise can modulate the excitability of the non-exercised upper-limb representation in the primary motor cortex (M1). Accumulating evidence demonstrates acute exercise affects measures of M1 intracortical excitability, with some studies also showing altered corticospinal excitability. However, the influence of distinct M1 interneuron populations on the modulation of intracortical and corticospinal excitability following acute exercise is currently unknown. We assessed the impact of an acute bout of leg cycling exercise on unique M1 interneuron excitability of a non-exercised intrinsic hand muscle using transcranial magnetic stimulation (TMS) in young adults. Specifically, posterior-to-anterior (PA) and anterior-to-posterior (AP) TMS current directions were used to measure the excitability of distinct populations of interneurons before and after an acute bout of exercise or rest. Motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) were measured in the PA and AP current directions in M1 at two time points separated by 25 min of rest, as well as immediately and 30 min after a 25-minute bout of moderate-intensity cycling exercise. Thirty minutes after exercise, MEP amplitudes were significantly larger than other timepoints when measured with AP current, whereas MEP amplitudes derived from PA current did not show this effect. Similarly, SICI was significantly decreased immediately following acute exercise measured with AP but not PA current. Our findings suggest that the excitability of unique M1 interneurons are differentially modulated by acute exercise. These results indicate that M1 interneurons preferentially activated by AP current may play an important role in the exercise-induced modulation of intracortical and corticospinal excitability.

The Dynamics of the Anaerobic Energy Contribution During a Simulated Mass-Start Competition While Roller-Ski Skating on a Treadmill.

The purposes of this study were: 1) to investigate the anaerobic energy contribution during a simulated cross-country (XC) skiing mass-start competition while roller-ski skating on a treadmill; 2) to investigate the relationship between the recovery of the anaerobic energy reserves and performance; and 3) to compare the gross efficiency (GE) method and maximal accumulated oxygen deficit (MAOD) to determine the anaerobic contribution. Twelve male XC skiers performed two testing days while roller skiing on a treadmill. To collect submaximal data necessary for the GE and MAOD method, participants performed a resting metabolism measurement, followed by low-intensity warm up, 12 submaximal 4-min bouts, performed using three different skating sub-techniques (G2 on a 12% incline, G3 on 5% and G4 on 2%) on three submaximal intensities on day 1. On day 2, participants performed a 21-min simulated mass-start competition on varying terrain to determine the anaerobic energy contribution. The speed was fixed, but when participants were unable to keep up, a 30-s rest bout was included. Performance was established by the time to exhaustion (TTE) during a sprint at the end of the 21-min protocol. Skiers were ranked based on the number of rest bouts needed to finish the protocol and TTE. The highest GE of day 1 for each of the different inclines/sub-techniques was used to calculate the aerobic and anaerobic contribution during the simulated mass start using the GE method and two different MAOD approaches. About 85–90% of the required energy during the simulated mass-start competition (excluding downhill segments) came from the aerobic energy system and ~10–15% from the anaerobic energy systems. Moderate to large Spearman correlation coefficients were found between recovery of anaerobic energy reserves and performance rank (rs = 0.58–0.71, p < 0.025). No significant difference in anaerobic work was found between methods/approaches (F(1.2,8.5) = 3.2, p = 0.10), while clear individual differences existed. In conclusion, about 10–15% of the required energy during the periods of active propulsion of a 21-min simulated mass-start competition came from the anaerobic energy systems. Due to the intermittent nature of XC skiing, the recovery of anaerobic energy reserves seems highly important for performance. To assess the anaerobic contribution methods should not be used interchangeably.

Breaking up prolonged sitting with a 6 min walk improves executive function in women and men esports players: a randomised trial

ObjectiveThe effect of prolonged sitting on executive function and performance in competitive esports players are unknown. This study aimed to evaluate executive function following a 6 min bout of walking...

Predicting Alzheimer's Disease from Combined Slow Gait and Low Activity Fragmentation - is Activity Fragmentation Always Bad?

Background: Among older people, slow walking is a mild predictor of Alzheimer's disease (AD). However, studies that assessed this association did not consider slow walking may have different causes and that the increased risk of AD may be limited to a subgroup. We hypothesized that individuals with slow walking who show frequent alternative bouts of activity and rest are more likely to have non-neurological causes of slow walking, while those who fail to use this compensatory strategy despite slow walking are more likely to have neurological causes that put them at higher risk of AD. Methods: We analyzed data on gait speed and activity fragmentation (AF) by accelerometry from 505 initially cognitively normal persons aged 60 and older (51%women, 24%Black). New diagnoses of mild cognitive impairment (MCI) or AD were adjudicated over a mean of 7·2-years. Associations of gait speed, AF, and their interaction with incident MCI/AD were evaluated by Cox proportional-hazards models, adjusted for covariates. Findings: MCI/AD developed in 64 participants. Each 0·05m/sec slower gait speed was associated with 8% higher risk of MCI/AD (p=0·03). AF alone was not associated with MCI/AD risk (p>0·05), but we found a significant “gait*AF” interaction (p=0·02). At low AF (-1SD), each 0·05 m/sec slower gait speed was associated with 16% higher risk of MCI/AD, while at higher AF (+1SD), gait speed did not predict MCI/AD. Among those with slow gait, higher AF was associated with less decline in pegboard dominant hand performance, higher odds of having lower extremity osteoarthritis, and higher cardiopulmonary burden. Interpretation: Frequent rests among slow walkers are associated with lower risk of future MCI/AD, perhaps because this behavioral strategy indicates lower likelihood of subclinical brain damage. On the contrary, failing to fragment activity in the face of impaired mobility may indicate subclinical brain damage and, therefore, is predictive of MCI/AD. Funding: This study was supported in part by the Intramural Research Program of the National Institute on Aging. Declaration of Interest: None declared. Ethical Approval: The BLSA protocol was approved by the Institutional Review Board of the National Institutes of Health. Participants provided written informed consent at each BLSA visit.

Restless nights? Nocturnal activity as a useful indicator of adaptability of shelter housed dogs

Shelter dogs face the challenge of adapting to a kennel environment. Individual differences in adaptation are known to exist. Resting patterns might be indicative of adaptability to such a novel environment, but need to be evaluated for its usefulness, like every potentially physiological and behavioural parameter. Here, we evaluated nocturnal activity patterns of dogs as indicators of adaptability to novel environments. We measured nocturnal activity (3-axial accelerometer, the Actical®) and two physiological stress parameters, i.e. urinary cortisol/creatinine ratio (UCCR) and body weight in 29 dogs relinquished to a shelter (SD group) in the first two days after intake at the shelter (n = 29), after a 12-day habituation period in the shelter (n = 28) and >6 weeks post-adoption (n = 17). A control group of 29 pet dogs kept at home (CPD group), matching the SD group characteristics, was also assessed for its nocturnal activity and UCCR. Linear mixed model analysis, t-tests and Friedman tests were used to analyse the data.The main findings are: 1) the SD group exhibited higher nocturnal activity (total activity counts, activity duration and number of rest bouts) the first two nights after intake than on night 12, with decreasing inter-individual variances. Compared to the CPD group they showed higher nocturnal activity on night 1 (all p < 0.001) and night 12 (all p ≤ 0.001) except for total activity counts on night 12. We found no ‘first-night effect’, where sleep is disturbed during the first night; nocturnal activity in the shelter did not significantly differ between nights 1 and 2 in the shelter. 2) In line with literature findings, SD group UCCRs were higher shortly after intake than after a 12-day habituation period and after adoption, and higher than in the CPD group. 3) An interaction was found between weight class and both nocturnal activity and UCCR levels: in their first days in the shelter, smaller dogs showing higher levels than larger dogs. 4) Dogs in the SD group lost, on average, 5% of their body weight between intake and the two-week habituation period.In conclusion, nocturnal activity, as measured by an accelerometer, may be a valid parameter to monitor adaptability of dogs to a kennel environment. Monitoring nocturnal activity in this way can be a useful and cost-effective additional indicator for assessing dog welfare.

Effects of Alpha‐adrenergic Receptors Blockade on Cardiovascular Responses to Acute Exercise and Isolated Metaboreflex in Postmenopausal Women

Postmenopausal women (PMW) have higher cardiovascular risk when compared to younger women (YM). Nevertheless, acute response to exercise may characterize an additional risk to PMW. One possible mechanism for an increased cardiovascular risk could be the constrictor effect of the alpha-adrenergic receptors (α-AR). Thus, we aimed to test the hypothesis that the contribution of the α-AR in the cardiovascular responses to exercise is greater in PMW when compared to YW. We measured heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), and total vascular resistance (TVR) in 7 YW (24±5 years;24±2kg∙m-2) and 7 PMW (59±4 years;25±3kg∙m-2), during three-minutes bouts of rest, hand grip exercise, isolated metaboreflex and recovery, respectively, in a control session and after α-AR blockade by oral administration of prazosin. HR increased during exercise in both groups but was blunted in PMW (YW: Δ28±15bpm; PMW: Δ15±7bpm; p<0.05). The α-AR blockade increased HR throughout the protocol (p<0.01), and the response to exercise was similar to the control condition (YW: Δ34±14bpm; PMW: Δ13±9bpm; p<0.05). During metaboreflex activation, HR was similar to resting values in both groups, in the control session (YW: Δ4±5bpm; PMW: Δ2±2bpm; p=0.11) and after the α-AR blockade (YW: Δ7±7bpm; PMW: Δ0±4bpm; p<0.05). MAP increased during exercise in both groups (YW: Δ33±10mmHg; PMW: Δ35±12mmHg; p=0.65). The α-AR blockade decreased MAP throughout the protocol (p<0.05) and the response to exercise was similar to the control session (YW: Δ22±16mmHg; PMW: Δ28±12mmHg; p=0.65). The metaboreflex activation kept the MAP elevated in both groups, in the control session (YW: Δ24±10mmHg; PMW: Δ26±7mmHg; p=0.65), while after the blockade, the increase was blunted when compared to the control session (YW: Δ6±20mmHg; PMW: Δ19±13mmHg; p=0.65). Exercise increased CO only in YW (YW: Δ2.3±1.6 l∙min-1; PMW: Δ0.9±1.4 l∙min-1; p<0.05). The α-AR blockade did not change CO throughout the protocol (p=0.21), with the response to exercise similar to the control condition (YW: Δ2.8±1.0 l∙min-1; PMW: Δ1.0±1.3 l∙min-1; p<0.05). During metaboreflex activation, CO increased only in PMW in the control session (YW: Δ1.1±0.8 l∙min-1; PMW: Δ0.4±0.6 l∙min-1; p<0.05), and after the α-AR blockade (YW: Δ0.4±2.6 l∙min-1; PMW: Δ-0.3±1.7 l∙min-1; p<0.05). Exercise increased TVR only in PMW (YW: Δ0±5mmHg∙l∙min-1; PMW: Δ4±4mmHg∙l∙min-1; p <0.05). The α-AR blockade decreased TVR throughout the protocol (p<0.05), but the response to exercise was similar to the control condition (YW: Δ-2±1mmHg∙l∙min-1; PMW: Δ3±3mmHg∙l∙min-1; p<0.05). The metaboreflex activation increased TVR only in PMW, in the control session, (YW: Δ1±3mmHg∙l∙min-1; PMW: Δ5±3mmHg∙l∙min-1; p<0.05), and after the α-AR blockade (YW: Δ-3±5mmHg∙l∙min-1; PMW: 1±8mmHg∙l∙min-1; p<0.05). We observed that PMW presents a peripheral vasoconstrictor response to exercise and metaboreflex activation when compared to YW, which seemed not to be driven by the α-AR vasoconstriction. Additionally, the adjustments in blood pressure were due to CO in YW and relied on TVR in PMW.

Activity of loggerhead turtles during the U-shaped dive: insights using angular velocity metrics

Understanding the behavioural ecology of endangered taxa can inform conservation strategies. The activity budgets of the loggerhead turtle Caretta caretta are still poorly understood because many tracking methods show only horizontal displacement and ignore dives and associated behaviours. However, time-depth recorders have enabled researchers to identify flat, U-shaped dives (or type 1a dives) and these are conventionally labelled as resting dives on the seabed because they involve no vertical displacement of the animal. Video- and acceleration-based studies have demonstrated this is not always true. Focusing on sea turtles nesting on the Cabo Verde archipelago, we describe a new metric derived from magnetometer data, absolute angular velocity, that integrates indices of angular rotation in the horizontal plane to infer activity. Using this metric, we evaluated the variation in putative resting behaviours during the bottom phase of type 1a dives for 5 individuals over 13 to 17 d at sea during a single inter-nesting interval (over 75 turtle d in total). We defined absolute resting within the bottom phase of type 1a dives as periods with no discernible acceleration or angular movement. Whilst absolute resting constituted a significant proportion of each turtle’s time budget for this 1a dive type, turtles allocated 16-38% of their bottom time to activity, with many dives being episodic, comprised of intermittent bouts of rest and rotational activity. This implies that previously considered resting behaviours are complex and need to be accounted for in energy budgets, particularly since energy budgets may impact conservation strategies.

Acute effects of highly intense interval and moderate continuous exercise on the modulation of neural oscillation during working memory

This study investigated the effects of high-intensity interval training (HIIT) and moderate-intensity continuous exercise (MICE) on behavioral performance and neural correlates of working memory. Thirty-six 18–30 years adults were recruited to perform a 20-min bout of HIIT, MICE, and rest on separate days in counterbalanced order. Following interventions, frontal alpha event-related desynchronization (ERD) was measured during a modified Sternberg task requiring varying amounts of working memory (3-, 5-, 7-letter tasks). Behavioral analyses showed a condition effect, indicating shorter response times following HIIT compared to rest. Analysis of frontal alpha ERD showed an interaction of condition and task, indicating no differences across tasks following rest but a task effect following HIIT and MICE, with frontal alpha ERD increasing in the 7-letter task compared with the 3-letter task. Following HIIT, this task-related contrast of frontal alpha ERD extended to the time period when memory retrieval occurred. Although both HIIT and MICE resulted in alterations in neuroelectric underpinnings of memory encoding and retention in response to increased memory load, only HIIT enhanced the processing speed and brain activation during memory retrieval. These findings provide evidence for potential applications of exercise to enhance working memory and the role of exercise type to such effect.

Renal Stress Responses To Work In The Heat Comparing Different Hydration Regimens

Workplace safety organizations recommend that workers predicted to incur heavy sweat loss should consume a ‘sport drink’ during work. These sugar-sweetened beverages (SSB) often include fructose, which can lead to acute kidney injury (AKI), especially when combined with hypohydration. PURPOSE: Investigate the effect of SSB on renal stress in response to simulated industrial work in the heat, while maintaining euhydration. METHODS: Twenty male participants (24 ± 2y, 179 ± 6cm, 24.7 ± 9.0% body fat) completed two randomized, matched trials of simulated industrial work (2-hr total; two 45-min work and two 15-min rest bouts) in the heat (30oC, 55% RH). Equal amounts of SSB or placebo were provided during rest and within 2-hr of completing work. Urine specific gravity (USG), heart rate (HR), and rectal temperature (Trec) were monitored throughout trials. Serum [Na+], hemoglobin, and hematocrit levels were measured at baseline, pre- and post-work, and 16-hr post-work. Urinary kidney injury molecule-1 (uKIM-1) and urinary neutrophil gelatinase-associated lipocalin (uNGAL) were measured pre- and post-work, 3-hr and 16-hr post-work. Total urine volume was measured for 16-hrs following work. Change in plasma volume (ΔPV) was calculated using the Dill & Costill equation. RESULTS: There was no significant trial difference in USG (p=.277) or HR (p=.209), but post-work (p≤.011) and 16-hr post-work USG were elevated compared to baseline (p=.043) and 3-hr post-work (p=.001). There was no difference in maximum Trec achieved between trials (SSB 38.84 ± 0.52oC; placebo 38.68 ± 0.40oC; p=.330). Serum [Na+] was elevated post-work compared to baseline and 16-hr post-work (p=.006), but there was no trial difference (p=.612). There was no trial difference in hemoglobin (p=.650) or hematocrit (p=.637). uKIM-1 was elevated post-work and 16-hr post-work compared to baseline (p≤.028) and 3-hr post-work (p≤.009), but showed no trial difference (p=.126). uNGAL 3-hr post-work was significantly lower than baseline (p=.011), but showed no trial difference (p=.992). There was no significant trial difference in total urine volume (p=.277) or ΔPV (p=.098). CONCLUSION: These findings indicate that beverage type did not affect renal stress biomarkers following simulated industrial work in the heat when euhydration was maintained.

160 Defining a role for CREB in hair follicle stem cell metabolism

Hair follicle stem cells (HFSCs) are multipotent epithelial stem cells that undergo cyclical bouts of growth and rest. They reside in a niche called the bulge and aid in wound healing, regulate the hair cycle, and produce new hair shafts every round of the hair cycle. The transcription factor, cyclic AMP (cAMP)-responsive element binding protein (CREB) plays a role in cell proliferation, differentiation, and is involved in the G-protein-coupled receptor (GPCR) signaling pathway. In vivo experiments on murine dorsal skin revealed that the phosphorylated, active form of CREB can be induced in the bulge upon topical treatment with a variety of compounds that facilitate downstream CREB activity such as cAMP, forskolin, and phosphodiesterase inhibitors.

Regulation of Rest, Rather Than Activity, Underlies Day-Night Activity Differences in Mice.

The suprachiasmatic nucleus (SCN), which serves as the central pacemaker in mammals, regulates the 24-h rhythm in behavioral activity. However, it is currently unclear whether and how bouts of activity and rest are regulated within the 24-h cycle (i.e., over ultradian time scales). Therefore, we used passive infrared sensors to measure temporal behavior in mice housed under either a light–dark (LD) cycle or continuous darkness (DD). We found that a probabilistic Markov model captures the ultradian changes in the behavioral state over a 24-h cycle. In this model, the animal’s behavioral state in the next time interval is determined solely by the animal’s current behavioral state and by the “toss” of a proverbial “biased coin.” We found that the bias of this “coin” is regulated by light input and by the phase of the clock. Moreover, the bias of this “coin” for an animal is related to the average length of rest and activity bouts in that animal. In LD conditions, the average length of rest bouts was greater during the day compared to during the night, whereas the average length of activity bouts was greater during the night compared to during the day. Importantly, we also found that day-night changes in the rest bout lengths were significantly greater than day-night changes in the activity bout lengths. Finally, in DD conditions, the activity and rest bouts also differed between subjective night and subjective day, albeit to a lesser extent compared to LD conditions. The ultradian regulation represented by the model does not result in ultradian rhythms, although some weak ultradian rhythms are present in the data. The persistent differences in bout length over the circadian cycle following loss of the external LD cycle indicate that the central pacemaker plays a role in regulating rest and activity bouts on an ultradian time scale.

Walking effects on memory in children: Implications for individual differences in BMI

BackgroundRecent evidence suggests improvements in memory performance following a single bout of physical activity in young children. However, few investigations have explored individual differences associated with these activity-induced changes in memory performance. ObjectivesThe present study investigated the effects of acute physical activity on recognition memory during and after treadmill walking in preadolescent children (n = 39; 24 females) with further exploration of individual differences in body mass index (BMI). MethodsWord recognition memory performance was assessed during and after the cessation of a moderate bout of walking (60% heart rate max; 20-min duration) or seated rest on separate days. ResultsChildren demonstrated unaltered word recall performance during walking compared to seated rest. Additionally, performance after walking revealed greater improvements in primacy accuracy (probability of correctly identifying the first ten words) relative to during walking and after seated rest. Additionally, evaluating only children who are overweight/obese (≥85th BMI percentile) revealed greater improvements in primacy accuracy following the walking bout with no effect observed for the normal weight group. ConclusionsTogether, these findings demonstrate that single bouts of walking are more effective for improving memory performance than non-active rest periods of a similar duration and may be enhanced to a greater degree among children who are overweight/obese. Such findings add to the growing body of literature supporting the need for active opportunities among all youth and further indicate the importance of advancing such opportunities among overweight/obese children to improve memory performance along with physical health.